ABS advice on finding a low carbon strategy

There is much to read about different approaches to low carbon shipping, but very little of it actually guides you, as a tanker operator, as to what you should do. ABS is aiming to fill this gap.

A starting point for each shipping company could be to follow IMO’s targets of reducing carbon intensity by 40 per cent by 2030 and 70 per cent by 2050, says Sotirios Mamalis, manager sustainability, fuels and technology with ABS. Each company will have its own roadmap to do this, based on the composition of its fleet and operations.

For example, ABS designed a model for a shipping company operating 10 bulk carriers today (2020). It could achieve the 2030 target first by reducing speed of all vessels by one knot. In 2023, it could replace three of the vessels with new LNG fuelled vessels (or retrofit 3 of the vessels to run on LNG). In 2025, it could introduce biofuel into 3 of the other vessels. This would add up to a 49 per cent reduction in CO2 emissions over 2020 to 2030.

We don’t need to change everything. ABS predicts that by 2050, 40 per cent of maritime fuels will still be oil based, while 35 per cent will be zero carbon fuels, either hydrogen or ammonia. A smaller fraction will be others, such as biofuels, methanol, LNG and LPG.


The most important method of reducing CO2 emissions is different fuel types, Mr Mamalis said. The company divides the fuel options into 3 pathways, light gas, heavy gas and biosynthetic liquid.

The light gas pathway starts with LNG, then moves to LNG created from bio or renewable electricity methods, then hydrogen.

LNG technology is established, and has a lower CO2 compared to oil, Mr Mamalis says. It means getting to grips with fuels which are stored in a different state to the one in which they are used (liquefied to cryogenic temperature, in this case). The engine technology is established and being improved. Vessels equipped for using LNG can transition to using bio or renewable electricity methane, ultimately hydrogen.

A challenge with LNG fuels is the methane emissions, which can come from the LNG production process or from methane ‘slip’ out of the engine. Methane is a stronger greenhouse gas than CO2, so a small amount of methane emissions can counter larger cuts in CO2 emissions from using LNG rather than liquid fuels.

The heavy gas pathway starts with LPG, then moves to bio and renewable electricity created fuels, including methanol, and ammonia.

LPG is currently only used as a fuel in LPG carriers (which burn their cargo for propulsion). There can be similar challenges to LNG for fuel containment and gas supply systems. It is possible to produce LPG and methanol for renewable energy. Ammonia “seems to be promising,” he says.

The bio-synthetic liquids family starts with biodiesel, and moves to gas-to-liquid fuels, and 2nd / 3rd generation biofuels. A benefit is that they can be used with existing diesel engines, with almost no modifications.

The CO2 from combustion is the same as with standard diesel, so it is very important to look closely at the lifecycle assessment – how much CO2 is taken from the atmosphere as the biofuels are grown (and what would be happening if they had not been planted), says Georgios Plevrakis, ABS director of global sustainability.

One fuel which may come into use is dimethyl ether, an isomer of ethanol, which is already used in heavy duty trucks. It can be used in diesel engines with very few modifications. It can be made from synthesis gas, using electricity from renewables as the energy input.

Mr Plevrakis sees that electrification could be a “common denominator” in future vessel designs – perhaps all vessels will convert their fuel to electrical energy and use that to power the vessel. This also enables the vessel to easily switch to external electrical energy when berthed.

The most mature of these three fuel pathways is the light gas since LNG vessels have already done millions of running hours. But there is plenty more to be solved achieving wider adoption of LNG, and further decarbonising of it, he said.


In terms of vessel operations, ABS sees that weather routing and “just in time arrival” are two useful technologies.

Weather routing means finding the best route for the vessel, in order to avoid bad weather, which means higher fuel consumption per mile. Just in time arrival means planning the vessel’s arrival at a berth exactly as the berth becomes available. If you arrive early and have to wait, it means you went faster (and burned more fuel) than you needed to.

Just in time arrival is complicated because it requires input and co-ordination of multiple groups – shipping companies and port operators, but also freight handling companies, customs and other regulatory bodies have input into when a vessel is allowed to leave, thus freeing up the berth for the next one. But despite this complexity, “it is worth pursuing because of benefit,” Mr Mamalis says.

What zero CO2 looks like

To explore what a true zero CO2 vessel might look like, ABS built two designs for a 6,600 dwt chemical carrier with a 3MW electric propeller motor.

The first design uses ammonia fuel. It has 510m3 of ammonia storage onboard, in two “Type C” cylindrical pressure vessels. This leaves space for the vessel to carry 7,700m3 of cargo, and a range of 4,200 nautical miles. The ammonia provides energy for a 3.5MW solid oxide fuel cell, which generates electricity to be stored in a 15 MWH battery back, to run the propeller.

The second design stores energy only in batteries. It has a 215 MWH lithium battery pack. This takes up much more space otherwise used for cargo, only leaving 4450m3 space for cargo. The range is also much reduced, to 720 nautical miles.




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